From patchwork Thu Jun 28 11:59:08 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 10493681 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E7A4A6022E for ; Thu, 28 Jun 2018 11:59:21 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D32AE29C26 for ; Thu, 28 Jun 2018 11:59:21 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C796829C33; Thu, 28 Jun 2018 11:59:21 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 63EDA29C26 for ; Thu, 28 Jun 2018 11:59:21 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C5C636ED1C; Thu, 28 Jun 2018 11:59:20 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1B8636ED1C for ; Thu, 28 Jun 2018 11:59:18 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from haswell.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 12187117-1500050 for multiple; Thu, 28 Jun 2018 12:59:09 +0100 Received: by haswell.alporthouse.com (sSMTP sendmail emulation); Thu, 28 Jun 2018 12:59:08 +0100 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Thu, 28 Jun 2018 12:59:08 +0100 Message-Id: <20180628115908.31933-1-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180627210712.25428-6-chris@chris-wilson.co.uk> References: <20180627210712.25428-6-chris@chris-wilson.co.uk> X-Originating-IP: 78.156.65.138 X-Country: code=GB country="United Kingdom" ip=78.156.65.138 Subject: [Intel-gfx] [PATCH v3] drm/i915/execlists: Reset CSB write pointer after reset X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" X-Virus-Scanned: ClamAV using ClamSMTP On HW reset, the HW clears the write pointer (to 0). But since it also writes its first CSB entry to slot 0, we need to reset the write pointer back to the element before (so the first entry we read is 0). This is required for the next patch, where we trust the CSB completely! v2: Use _MASKED_FIELD v3: Store the reset value, so that we differentiate between mmio/hwsp transparently and without pretense. Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Reviewed-by: Tvrtko Ursulin --- drivers/gpu/drm/i915/intel_lrc.c | 23 +++++++++++++++++++++-- drivers/gpu/drm/i915/intel_ringbuffer.h | 9 +++++++++ 2 files changed, 30 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 8531a5b6f6ff..49bf5048043c 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -884,6 +884,21 @@ static void reset_irq(struct intel_engine_cs *engine) clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted); } +static void reset_csb_pointers(struct intel_engine_execlists *execlists) +{ + /* + * After a reset, the HW starts writing into CSB entry [0]. We + * therefore have to set our HEAD pointer back one entry so that + * the *first* entry we check is entry 0. To complicate this further, + * as we don't wait for the first interrupt after reset, we have to + * fake the HW write to point back to the last entry so that our + * inline comparison of our cached head position against the last HW + * write works even before the first interrupt. + */ + execlists->csb_head = execlists->csb_write_reset & 0xff; + WRITE_ONCE(*execlists->csb_write, execlists->csb_write_reset); +} + static void execlists_cancel_requests(struct intel_engine_cs *engine) { struct intel_engine_execlists * const execlists = &engine->execlists; @@ -1970,7 +1985,7 @@ static void execlists_reset(struct intel_engine_cs *engine, __unwind_incomplete_requests(engine); /* Following the reset, we need to reload the CSB read/write pointers */ - engine->execlists.csb_head = GEN8_CSB_ENTRIES - 1; + reset_csb_pointers(&engine->execlists); spin_unlock_irqrestore(&engine->timeline.lock, flags); @@ -2469,7 +2484,6 @@ static int logical_ring_init(struct intel_engine_cs *engine) upper_32_bits(ce->lrc_desc); } - execlists->csb_head = GEN8_CSB_ENTRIES - 1; execlists->csb_read = i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)); if (csb_force_mmio(i915)) { @@ -2477,13 +2491,18 @@ static int logical_ring_init(struct intel_engine_cs *engine) (i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_BUF_LO(engine, 0))); execlists->csb_write = (u32 __force *)execlists->csb_read; + execlists->csb_write_reset = + _MASKED_FIELD(GEN8_CSB_WRITE_PTR_MASK, + GEN8_CSB_ENTRIES - 1); } else { execlists->csb_status = &engine->status_page.page_addr[I915_HWS_CSB_BUF0_INDEX]; execlists->csb_write = &engine->status_page.page_addr[intel_hws_csb_write_index(i915)]; + execlists->csb_write_reset = GEN8_CSB_ENTRIES - 1; } + reset_csb_pointers(execlists); return 0; diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h index 970dbb3c9812..6ec7c019b5d9 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.h +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h @@ -304,6 +304,15 @@ struct intel_engine_execlists { */ unsigned int csb_head; + /** + * @csb_write_reset: reset value for CSB write pointer + * + * As the CSB write pointer maybe either in HWSP or as a field + * inside an mmio register, we want to reprogram it slightly + * differently to avoid later confusion. + */ + u32 csb_write_reset; + /** * @csb_read: control register for Context Switch buffer *